Check Whether a String Is Not Null and Not Empty

Check whether a string is not null and not empty

What about isEmpty() ?

if(str != null && !str.isEmpty())

Be sure to use the parts of && in this order, because java will not proceed to evaluate the second part if the first part of && fails, thus ensuring you will not get a null pointer exception from str.isEmpty() if str is null.

Beware, it's only available since Java SE 1.6. You have to check str.length() == 0 on previous versions.

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To ignore whitespace as well:

if(str != null && !str.trim().isEmpty())

(since Java 11 str.trim().isEmpty() can be reduced to str.isBlank() which will also test for other Unicode white spaces)

Wrapped in a handy function:

public static boolean empty( final String s ) {
  // Null-safe, short-circuit evaluation.
  return s == null || s.trim().isEmpty();
}

Becomes:

if( !empty( str ) )

How to check a string is not null?

Checking for null is done via if (string != null)

If you want to check if its null or empty - you'd need if (string != null && !string.isEmpty())

I prefer to use commons-lang StringUtils.isNotEmpty(..)

How to check if a value is not null and not empty string in JS

If you truly want to confirm that a variable is not null and not an empty string specifically, you would write:

if(data !== null && data !== '') {
   // do something
}

Notice that I changed your code to check for type equality (!==|===).

If, however you just want to make sure, that a code will run only for "reasonable" values, then you can, as others have stated already, write:

if (data) {
  // do something
}

Since, in javascript, both null values, and empty strings, equals to false (i.e. null == false).

The difference between those 2 parts of code is that, for the first one, every value that is not specifically null or an empty string, will enter the if. But, on the second one, every true-ish value will enter the if: false, 0, null, undefined and empty strings, would not.

How to check for Is not Null And Is not Empty string in SQL server?

If you only want to match "" as an empty string

WHERE DATALENGTH(COLUMN) > 0 

If you want to count any string consisting entirely of spaces as empty

WHERE COLUMN <> '' 

Both of these will not return NULL values when used in a WHERE clause. As NULL will evaluate as UNKNOWN for these rather than TRUE.

CREATE TABLE T 
  ( 
     C VARCHAR(10) 
  ); 

INSERT INTO T 
VALUES      ('A'), 
            (''),
            ('    '), 
            (NULL); 

SELECT * 
FROM   T 
WHERE  C <> ''

Returns just the single row A. I.e. The rows with NULL or an empty string or a string consisting entirely of spaces are all excluded by this query.

SQL Fiddle

Check if a string is not NULL or EMPTY

if (-not ([string]::IsNullOrEmpty($version)))
{
    $request += "/" + $version
}

You can also use ! as an alternative to -not.

How to check a string that not empty in java?

You can see if the characters match

if (str.equals ("")) {
  // true
}

if (str3.equals ("   ")) {
  // true
}

How do I check for an empty/undefined/null string in JavaScript?

Empty string, undefined, null, ...

To check for a truthy value:

if (strValue) {
    // strValue was non-empty string, true, 42, Infinity, [], ...
}

To check for a falsy value:

if (!strValue) {
    // strValue was empty string, false, 0, null, undefined, ...
}

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Empty string (only!)

To check for exactly an empty string, compare for strict equality against "" using the === operator:

if (strValue === "") {
    // strValue was empty string
}

To check for not an empty string strictly, use the !== operator:

if (strValue !== "") {
    // strValue was not an empty string
}

Best way to verify string is empty or null

Haven't seen any fully-native solutions, so here's one:

return str == null || str.chars().allMatch(Character::isWhitespace);

Basically, use the native Character.isWhitespace() function. From there, you can achieve different levels of optimization, depending on how much it matters (I can assure you that in 99.99999% of use cases, no further optimization is necessary):

return str == null || str.length() == 0 || str.chars().allMatch(Character::isWhitespace);

Or, to be really optimal (but hecka ugly):

int len;
if (str == null || (len = str.length()) == 0) return true;
for (int i = 0; i < len; i++) {
  if (!Character.isWhitespace(str.charAt(i))) return false;
}
return true;

One thing I like to do:

Optional<String> notBlank(String s) {
  return s == null || s.chars().allMatch(Character::isWhitepace))
    ? Optional.empty()
    : Optional.of(s);
}

...

notBlank(myStr).orElse("some default")

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